Effects of Electroacupuncture on Pain Threshold of Laboring Rats and the Expression of Norepinephrine Transporter and α2 Adrenergic Receptor in the Central Nervous System

Abstract

To observe the effects of electroacupuncture on pain threshold of laboring rats and the expression of norepinephrine transporter and α2 adrenergic receptor in the central nervous system to determine the mechanism of the analgesic effect of labor. 120 pregnant rats were divided into 6 groups: a control group, 4 electroacupuncture groups, and a meperidine group. After interventions, the warm water tail-flick test was used to observe pain threshold. NE levels in serum, NET, and α2AR mRNA and protein expression levels in the central nervous system were measured. No difference in pain threshold was observed between the 6 groups before intervention. After intervention, increased pain thresholds were observed in all groups except the control group with a higher threshold seen in the electroacupuncture groups. Serum NE levels decreased in the electroacupuncture and MP groups. Increases in NET and α2AR expression in the cerebral cortex and decreases in enlarged segments of the spinal cord were seen. Acupuncture increases uptake of NE via cerebral NET and decreases its uptake by spinal NET. The levels of α2AR are also increased and decreased, respectively, in both tissues. This results in a decrease in systemic NE levels and may be the mechanism for its analgesic effects.

Electroacupuncture for pain relief in labour inhibits spinal p38 MAPK-mediated prostaglandin E2 release and uterine prostaglandin E2 receptor expression in rats

“…Currently, more and more parturients hope to receive non-pharmacological analgesia because of the potential side effects of pharmacological analgesia including maternal apnoea and neonatal acidosis. 1,2 In this study, EA at Jiaji or SP6+LI4 significantly increased the pain threshold of rats in labour, which was consistent with past reports and our previous studies, 7–10 implying an analgesic effect of EA at Jiaji and SP6+LI4 on labour pain. It is well known that PGE2 is a key mediator of inflammation and contributes to pain secondary to inflammation and mechanical injury.…”

“…Additionally, there were no differences in pain threshold, serum PGE2 levels or expression of p38 MAPK and PLA2 in the lumbar spinal cord between EA at Jiaji and at SP6+LI4, indicating similar effects and mechanisms of EA at these different sites. We have reported that EA relieves labour pain through the involvement of the spinal dynorphin/κ-opioid receptor system, central nervous norepinephrine transporter and α2 adrenergic receptor expression, 9,10 implying that EA relieves labour pain through multiple mechanisms. Moreover, EA regulates the release of opioids that have a close relationship with pain, 8,9,34 but the underlying mechanisms remain to be fully elucidated and need further study.…”

“…9 Moreover, EA reduced serum norepinephrine (NE) levels, increased protein and gene expression of NE transporter and α2 adrenergic receptor in the grey matter, but decreased their expression in the lumbar spinal cord. 10 However, the mechanisms by which EA relieves labour pain remain to be fully elucidated.…”

La electroacupuntura como alternativa en la inducción del parto en el embarazo postérmino

“…Numerosos estudios neuroquímicos realizados en diferentes especies de animales, demuestran que la EA también modula la síntesis y liberación de neurotransmisores, neurohormonas y otros mediadores químicos en diferentes circuitos neuronales situados por encima de la medula espinal en el SNC (Vixner et al, 2012;Hu et al, 2016). Por ejemplo, en los circuitos relacionados con el dolor y la analgesia, la EA modula la síntesis y liberación de los opioides endógenos, endorfinas, encefalinas y dinorfinas, así como también de la serotonina (5-HT), los cuales participan en su acción analgésica demostrada (Hu et al, 2016;Tang et al, 2016). También actúa modulando neurocircuitos límbicos relacionados Moberg et al, 1993;Qu & Zhou, 2006;Tang et al, 2016).…”

“…Por ejemplo, en los circuitos relacionados con el dolor y la analgesia, la EA modula la síntesis y liberación de los opioides endógenos, endorfinas, encefalinas y dinorfinas, así como también de la serotonina (5-HT), los cuales participan en su acción analgésica demostrada (Hu et al, 2016;Tang et al, 2016). También actúa modulando neurocircuitos límbicos relacionados Moberg et al, 1993;Qu & Zhou, 2006;Tang et al, 2016). Como vemos, estos mecanismos neurohumorales de la EA para desencadenar y mantener el trabajo de parto, constituyen una vía de acción larga e indirecta sobre el útero, que necesariamente implica la síntesis de neuromediadores y neurohormonas en los sitios correspondientes del SNC y su posterior liberación a la sangre para finalmente alcanzar y actuar en los receptores del útero.…”